Walk behind mower

ABSTRACT

Disclosed is a self propelled walk behind mower comprised of a tractor unit and a mowing deck. The tractor unit is hydrostatically driven with a unique control system whereby the forward speed of the tractor is set by operating an electric rocker switch with an operator&#39;s thumb. Hand levers are used to turn the tractor to the left and the right. The tractor unit comprises two drive wheels and a third wheel that is pivotally attached, letting the tractor unit stand upright when no implements are attached. Implements attach to the front of the tractor through a movable attachment so that the tractor and implement can closely follow the contour of the ground while keeping the operator controls in a convenient position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 60/391,057 entitled “Walk Behind Mower” byDean M. Walker, filed Jun. 21, 2002, the entire contents of which arespecifically incorporated herein by reference for all it discloses andteaches.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention pertains generally to walk-behind mowers andspecifically to walk-behind mowers that have electric speed control.

b. Description of the Background

Walk-behind mowers including a tractor unit and a mowing deck attachedto the front of the tractor have been commercially available for a longtime. Typically, the tractor has only two wheels and the mowing deck isrigidly connected to the forward end of the tractor. A seriousdisadvantage with such types of mowers is that the quality of cutting isnot as good as desired, since the mower can ‘scalp’ the grass in someareas and leave the grass too long in other areas because the mowingdeck is not able to closely follow the contour of the ground.

The operator controls for self-propelled walk behind mowers tend to bedifficult to use while meeting the requirements of safety andoperability. In some cases, the operator must continually grip two handlevers in order for the mower to move forward at a constant speed. Sucha system is prone to operator fatigue.

It would therefore be advantageous to provide a mower that moreaccurately follows the contour of a lawn during mowing and furtherprovides a set of operator controls that are not prone to operatorfatigue.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages and limitations of theprior art by providing a mower that has a deck removably attached to awalk behind, self-propelled tractor. The tractor has a set of operatorcontrols that includes a rocker switch that is used to set the forwardspeed of the tractor and two hand levers that are used to brake eachwheel individually for steering. The tractor is propelled usingindividual hydrostatic drives on each of two main drive wheels and has athird wheel pivotally mounted rearwardly that provides stability to thetractor when no implements are attached. The tractor has an articulatedmower deck mounted to the front. The arrangement is better able toclosely follow the contour of the ground during mowing of unevensurfaces and places the operator controls in a more comfortable andcontrollable position.

The present invention may therefore comprise a self propelled walkbehind mower comprising: a tractor unit having left and right drivewheels and a tail wheel pivotably mounted rearwardly of the drive wheelsfor stability, the tractor having an internal combustion engine mountedbetween the drive wheels and the tail wheel, the drive wheels beingindependently powered by left and right hand hydrostatic drive units,the tractor unit further having a forward end; and a mower deck havingtwo wheels pivotally mounted to the front of the mower deck, the mowerdeck mounted to the forward end of the tractor unit wherein the mowerdeck is able to pivot up and down and tilt side to side relative to thetractor unit such that the mower deck may follow the contour of theground.

The present invention may further comprise a control system for a selfpropelled walk behind mower comprising: a speed lever disposed to beoperated by the operator, the speed lever being connected to anactuator, a pair of adjustable stops moved in parallel by the actuator;a left lever being operably connected to a left stop and furtherconnected to a left hydrostatic drive unit, the left lever beingdisposed to be operated by an operator's left hand, the left hydrostaticdrive having a forward speed being limited by the obstruction of theleft stop against the adjustable stop, the left lever adapted to biasthe left stop against the adjustable stop and further being adapted toslow the left hydrostatic drive by the actuation of the left lever bythe operator; and a right lever being operably connected to a right stopand further connected to a right hydrostatic drive unit, the right leverbeing disposed to be operated by an operator's right hand, the righthydrostatic drive having a forward speed being limited by theobstruction of the right stop against the adjustable stop, the rightlever adapted to bias the right stop against the adjustable stop andfurther being adapted to slow the left hydrostatic drive by theactuation of the left lever by the operator.

The present invention may further comprise a method of controlling aself propelled walk behind mower comprising: activating a speed lever tomove an actuator, the actuator being connected to adjustable stops, theadjustable stops disposed to simultaneously move a left stop and a rightstop such that a left hydrostatic drive and a right hydrostatic driveconnected to a left drive wheel and a right drive wheel aresimultaneously activated to move the mower in a forward direction;activating a left lever that is operably connected to the lefthydrostatic drive and further limited in travel by the adjustable stops,the activating of the left lever causing the left hydrostatic drive toslow down, causing the mower to turn to the left; and activating a rightlever that is operably connected to the right hydrostatic drive andfurther limited in travel by the adjustable stops, the activating of theright lever causing the right hydrostatic drive to slow down, causingthe mower to turn to the right.

The advantages of the present invention are that the mower is betterable to follow the contour of the ground due to the articulatedconnection of the mower deck to the three wheeled tractor. Further, thepositioning of the operator controls while following various groundcontours is more comfortable and thus safer and less fatiguing. Thecontrol system for the mower allows for infinitely adjustable forwardspeed without requiring the operator to continually hold any handlesother than an operator presence switch, further decreasing the fatigueof the operator.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is an illustration of an embodiment of the present inventionshowing a tractor and an operator.

FIG. 2 is an illustration of a second view of an embodiment of thepresent invention showing a tractor and an operator.

FIG. 3 is an illustration of an embodiment of the present inventioncomprising a tractor and a mowing deck.

FIG. 4 is an illustration of the effect of the articulated arrangementof a tractor and a mowing deck.

FIG. 5 is an illustration of a rear view of an embodiment of the presentinvention.

FIG. 6 is an illustration of the underside of an embodiment of a tractorshowing the control linkages.

FIG. 7 is an illustration of an embodiment of the linkages used tocontrol the tractor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an embodiment of the present invention showing atractor 100 and an operator 102. The tractor 100 has a drive wheel 104and a third wheel 106 that pivots but is not driven or steered. Theengine 108 powers the tractor. The operator controls 110 are also shownin the present figure.

FIG. 2 illustrates a second view of an embodiment of the presentinvention showing a tractor 200, a first drive wheel 202, and a seconddrive wheel 204. The drive wheel 202 is powered by a hydro-axle 206 anddrive wheel 204 is powered by hydro-axle 208.

The hydro-axles 206 and 208 are powered by an engine and are controlledby an operator to direct the movement of the tractor 200. Thehydro-axles 206 and 208 may be capable of infinitely adjustable speedcontrol based on the input from the operator. Steering is achievedthrough differential speeds applied to the drive wheels 202 and 204. Thehydro-axles 206 and 208 may further be capable of reversing direction.In the case where one hydro-axle is moving in reverse and the otherhydro-axle is moving forward at the same speed, the tractor 200 may turnabout an axis defined at the midpoint of the axis of the two wheels 202and 204.

The deck attachment arms 210 and 212 along with the deck attachmentreceiver 214 may be used to attach a mowing deck or other implement onthe front of the tractor 200. The deck attachment arms 210 and 212 arepivotally attached to the tractor 200. The deck attachment receiver 214may receive a (i.e. compliant connector) whereby a mowing deck mayflexibly move with respect to the tractor 200. The compliant mechanismallows the deck to tip up and down and further tilt side to side tofollow the contour of the ground.

FIG. 3 illustrates an embodiment of the present invention comprising atractor 300 and a mowing deck 302. The mowing deck 302 is attached tothe tractor 300 by sliding the deck attachment arms shown in FIG. 2 intoreceivers such as receiver 304. The deck 302 is supported at the tractorend by the deck attachment arms and at the opposite end by wheels 306and 308. The suspension 310 couples the mower deck 302 to the tractor300.

The deck 302 is able to move up and down with respect to the tractor 300as well as rotate side to side to some extent. In the presentembodiment, the mower deck may articulate plus or minus about 5 degreeswith respect to the longitudinal vertical plane. The ability of the deckto follow the contour of the ground greatly enhances the mower's abilityto leave a consistent and aesthetically pleasing lawn over roughcontours.

The three wheeled design of the tractor 300 is such that the tractor isstable when no implements are attached. With the prior art two wheeledtractors, the tractor would tip over when not balanced by a mowing deckor other implement on the front. By having a third wheel, the drivewheels may be positioned as far forward as possible to give theimplement, such as a mower deck, increased ability to follow thecontours of the ground.

The third wheel further allows various implements of different weightsand balances to be attached to the tractor and still operate smoothly.If the third wheel were not present and a heavy implement were attachedto the front, the balance and feel of the machine would be drasticallydifferent than if the machine had a light weight implement, or none atall. Further, since the prior art machines are balanced differently fordifferent weight implements, there would be increased operator fatiguewith the prior art machines.

The deck 302 is able to articulate with respect to the tractor 300 alongthe horizontal plane. Since the tractor 300 is fully supported by twodrive wheels 312 and the third wheel 314, the operator controls 316 willstay in a more comfortable position when mowing over a crest of a hillor when traversing a low spot.

FIG. 4 illustrates the effect of the articulated arrangement of atractor 400 and a mowing deck 402. The operator 404 is in a comfortableposition with respect to the operator controls 406 as the tractor 400crests the hill 408. If the articulated arrangement were not present,the position of the tractor 400 may be illustrated by the phantomposition 410. In the phantom position 410, the operator controls 412would be significantly higher and more difficult to reach for theoperator 404 than in the present embodiment 400. When the mowertraverses a valley, the articulated arrangement of the tractor 400 andthe mowing deck 402 keeps the operator controls 406 in a much moreconvenient position for the operator 404.

FIG. 5 illustrates a rear view of an embodiment of the presentinvention. The tractor 500 is shown from the rear with a mower deck 502,a left drive wheel 504, a right drive wheel 506, and a third wheel 508.The operator controls 510 comprise left and right hand grips 512 and514, respectively, left and right hand controls 516 and 518, left andright operator presence levers 520 and 522, and a thumb switch 524.

The thumb switch 524 sets the forward speed control of the tractor 500.The thumb switch 524 is a three-position rocker switch movable by theoperator's right thumb. As the operator presses the switch 524 in theforward position, the tractor 500 moves forward faster. As the operatorreleases the switch 524 to the center position, the forward speed ismaintained. When the operator wishes to slow down, the rear position ofthe switch 524 may be pressed to slow down the tractor 500.

The hand controls 516 and 518 allow the operator to steer the tractor500 by slowing or reversing the wheel associated with the respectivehand control. For example, during forward motion, the operator maysqueeze the left hand control 516 to slow the left hand drive wheel 504and cause the tractor 500 to turn to the left. The sharpness of the turnis dictated by the amount that the operator grips the respective handcontrol. The hydro-axle system may have the capability of reversing thedrive wheels. In such a case, squeezing the hand control completely willcause the drive wheel to reverse direction, allowing the tractor 500 toexecute a zero radius turn. Likewise, simultaneously squeezing both handcontrols completely will cause the tractor 506 to move in reverse.

The PTO engagement lever 526 may be used to engage the power take offfor an implement such as the mower deck 502. The lever 526 may engage amechanical clutch mechanism that transmits power to the deck 502.

Left and right operator presence levers 520 and 522 may be connected inparallel such that only one switch is necessary for the tractor to sensethe operator presence. One or both of the levers 520 and 522 may benecessary for the tractor 500 to operate. For example, if the tractorwere moving forward and the operator removed both hands from thecontrols 510, the levers 520 and 522 would disengage and the tractorwould shut down or otherwise halt motion. When the PTO lever 526 isengaged, releasing both of the operator presence levers 520 and 522 willkill the engine and halt operation.

The left and right hand controls 516 and 518 are connected to left andright hand control linkages 528 and 530, respectively. The linkages 528and 530 are connected to the hydro-axles though a mechanism that setsthe forward speed of the hydro-axles simultaneously.

FIG. 6 illustrates the underside of an embodiment of a tractor 600. Theleft and right drive wheels 602 and 604 and the third wheel 606 areshown. Left and right hydro-axles 608 and 610 are connected to thewheels 602 and 604, respectively. The control linkages 612 and 614 arethe control linkages 528 and 530 shown in FIG. 5. The control linkages612 and 614 are connected to rotary links 616 and 618, which connect toconnecting links 620 and 622, which connect to the hydro-axle inputcontrols 624 and 626. This mechanism is the connection between thehandle grips operated by the operator and the hydro-axles that controlthe forward and reverse speeds of the tractor.

The rotary links 616 and 618 are mounted on a limiting shaft 628. Thelimiting shaft 628 has stops, not shown in the present figure, thatsimultaneously limit the amount of travel the rotary links 616 and 618can rotate. As the electric actuator 630 rotates the limiting shaft 628through the lever 632, the rotary links 616 and 618 move to a positionwhereby the connecting links 620 and 622, the input controls 624 and626, and thus the hydro-axles 608 and 610 are simultaneously engaged tomove forward. The electric thumb switch 524 of FIG. 5 may be connectedto the actuator 630 to change the forward speed of the tractor. At anytime that the tractor is in a forward motion, the hand levers may beactuated to slow the speed of the tractor, bring the tractor to a halt,or reverse the motion of the tractor.

The term hydro-axle refers to a hydrostatic drive with an integrated,load carrying axle. For the present embodiment, the hydro-axle offers acompact and cost efficient design. Those skilled in the arts wouldappreciate that alternative designs comprising a hydrostatic drive witha separate axle system would be possible while maintaining within thescope and intent of the present invention.

FIG. 7 illustrates an embodiment of the linkages used to control thetractor. The operator controls 702 comprise the left and right handgrips 704 and 706, operator presence levers 708 and 710, and controllevers 712 and 714. Control levers 712 and 714 are connected to controllinkages 716 and 718, respectively, that are connected to left and rightrotary linkages 720 and 722. Each rotary link 720 and 722 are connectedto connecting links 724 and 726 that connect to the independenthydro-axles not shown.

A limiting shaft 728 is shown in an exploded state in three pieces forclarity, but is rigidly connected in operation. The limiting shaft 728has left and right stop plates 730 and 732 as well as a link 734connected to an electric actuator 736.

The rotary link 720 is mounted on the limiting shaft 728 and comprisesan input arm 738, and output arm 740, and a stop plate 742. The stopplate 742 has an adjustment screw 744. When assembled, the stop plate742 and adjustment screw 744 is positioned to press against the limitingshaft stop plate 730.

When the electric actuator 736 moves, the stop plates 730 and 732 movesimultaneously against the stop plates 742 and 746 to limit the amountof travel of the stop plates 742 and 746. As the travel of therespective stop plates are changed, the position of the rotary links 720and 722 are changed, thusly changing the inputs to the independenthydro-axles and causing the tractor to change speed. Since the left andright hydro-axles are changed equally and simultaneously, the tractorwill move in a straight line. At any time the tractor is moving in astraight line, an operator may change the speed of one or both wheels byactuating the levers 712 or 714.

The stop plates 730 and 732 change the limit on the maximum forwardspeed of the respective wheel, thus the actuation of levers 712 or 714serve to slow the respective hydro-axle and thus the drive wheel. Thebenefit of the present embodiment is that the electric actuator 736 canbe used to set the forward speed of the tractor and the operator doesnot need to grip the control levers 712 and 714 during normal forwardspeed. Since the operator is not required to continually grip the levers712 and 714 during normal forward motion, the fatigue and discomfort ofother walk behind mowers is alleviated. Another benefit of the electricactuator 736 is that the forward speed can be adjusted to the operator'spreference. In some situations where tight turning may be critical, thespeed may be adjusted to be somewhat slow. In situations where longstretches of straight motion are required, the operator may adjust thespeed to be higher. As the operator approaches a turn, the speed can besimply lessened with a thumb switch such that the turn can be executedwithout difficulty.

Alternative arrangements for the forward speed control are possible. Inthe present embodiment, the operator uses an electric switch to actuatean electric actuator that moves two stops simultaneously. In otherembodiments, the operator may move a mechanical lever to directlyactuate the stops. Alternatively, hydraulic or other methods ofactuation are possible by those skilled in the arts while maintainingwithin the scope of the present invention.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

1. A self propelled walk behind mower comprising: a tractor unit havinga forward end and a rearward end that define a lengthwise direction; anengine mounted on said tractor unit; hydrostatic drives mounted to saidtractor unit that are driven by said engine; drive wheels coupled tosaid hydrostatic drives at said forward end of said tractor unit; athird wheel pivotally attached to said rearward end of said tractor unitthat allows said tractor unit to stand upright with respect to a planedefined by said drive wheels and said third wheel when no implements areattached to said tractor unit and is fully supported by said drivewheels and said third wheel; handles attached to said tractor unit thatextend rearwardly in said lengthwise direction, and that have controlsthat allow a user to control said tractor unit; deck attachment armsthat extend in a forward direction from said forward end of said tractorunit; a pivot attached to said forward end of said tractor unit and tosaid deck attachment arms that allow said deck attachment arms to pivotabout an axis that is transverse to said lengthwise direction; a mowingdeck having a forward end and a rearward end, and at least two frontwheels mounted on said forward end of said mowing deck; deck attachmentreceivers disposed at said rearward end of said mowing deck thatdetachably engage said deck attachment arms so that said mowing deckpivots with respect to said tractor unit about said transverse axis,said deck attachment having a compliant connector that allows saidmowing deck to flexibly move with respect to said tractor unit; and asuspension that detachably connects said mowing deck to said tractorunit and supports said rearward end of said mowing deck.
 2. The selfpropelled walk behind mower of claim 1 wherein said pivot furthercomprises: a pivot that operates in a range of approximately fivedegrees above and below said plane defined by said drive wheel and saidthird wheel.
 3. The self propelled walk behind mower of claim 1 whereinsaid hydro drives further comprise: a first hydro axle that is attachedto a first wheel and that powers said first wheel, so that said firstwheel rotates in a forward and reverse direction in response to an inputfrom an operator; and a second hydro axle that is attached to a secondwheel and that powers said second wheel so that said second wheelrotates in a forward and reverse direction in response to an input froman operator.
 4. The self propelled walk behind mower of claim 3 whereinsaid drive wheels are substantially aligned with said pivot in saidlengthwise direction at said forward end of said tractor.